From dd7000e06911c253e8d1da413536cfae4ab26a49 Mon Sep 17 00:00:00 2001
From: Pim Kunis <pim@kunis.nl>
Date: Sat, 24 Jul 2021 22:08:01 +0200
Subject: [PATCH] Add validation of auth events for events

---
 lib/matrix_server/room_server.ex      | 36 ++++++++++++++++++++++-----
 lib/matrix_server/state_resolution.ex | 29 +++++++++++++++++----
 2 files changed, 54 insertions(+), 11 deletions(-)

diff --git a/lib/matrix_server/room_server.ex b/lib/matrix_server/room_server.ex
index b9b3891..b1d4994 100644
--- a/lib/matrix_server/room_server.ex
+++ b/lib/matrix_server/room_server.ex
@@ -1,7 +1,9 @@
 defmodule MatrixServer.RoomServer do
   use GenServer
 
-  alias MatrixServer.{Repo, Room, Event, Account}
+  import Ecto.Query
+
+  alias MatrixServer.{Repo, Room, Event, Account, StateResolution}
   alias MatrixServerWeb.API.CreateRoom
 
   @registry MatrixServer.RoomServer.Registry
@@ -43,11 +45,33 @@ defmodule MatrixServer.RoomServer do
          %CreateRoom{room_version: room_version},
          room_id
        ) do
-    state_set =
-      Event.create_room(room_id, MatrixServer.get_mxid(localpart), room_version)
-      |> Repo.insert!()
-      |> MatrixServer.StateResolution.resolve(true)
+    create_room_event = Event.create_room(room_id, MatrixServer.get_mxid(localpart), room_version)
+    verify_event(create_room_event)
+    |> IO.inspect()
 
-    {:ok, state_set}
+    {:ok, %{}}
+  end
+
+  defp verify_event(%Event{auth_events: auth_event_ids} = event) do
+    # Check the following things:
+    # 1. TODO: Is a valid event, otherwise it is dropped.
+    # 2. TODO: Passes signature checks, otherwise it is dropped.
+    # 3. TODO: Passes hash checks, otherwise it is redacted before being processed further.
+    # 4. Passes authorization rules based on the event's auth events, otherwise it is rejected.
+    # 5. Passes authorization rules based on the state at the event, otherwise it is rejected.
+    # 6. TODO: Passes authorization rules based on the current state of the room, otherwise it is "soft failed".
+    if StateResolution.is_authorized_by_auth_events(event) do
+      auth_events =
+        Event
+        |> where([e], e.event_id in ^auth_event_ids)
+        |> select([e], {e.event_id, e})
+        |> Repo.all()
+        |> Enum.into(%{})
+      # TODO: make the state set a mapping to Event struct.
+      state_set = StateResolution.resolve(event, false)
+      StateResolution.is_authorized(event, state_set, auth_events)
+    else
+      false
+    end
   end
 end
diff --git a/lib/matrix_server/state_resolution.ex b/lib/matrix_server/state_resolution.ex
index 548ad93..305a606 100644
--- a/lib/matrix_server/state_resolution.ex
+++ b/lib/matrix_server/state_resolution.ex
@@ -12,7 +12,7 @@ defmodule MatrixServer.StateResolution do
     |> Map.put(:auth_events, ["create", "join_charlie", "b"])
   end
 
-  def resolve(%Event{room_id: room_id} = event, apply_state \\ false) do
+  def resolve(%Event{room_id: room_id} = event, apply_state) do
     room_events =
       Event
       |> where([e], e.room_id == ^room_id)
@@ -31,7 +31,7 @@ defmodule MatrixServer.StateResolution do
     state_sets =
       prev_event_ids
       |> Enum.map(&room_events[&1])
-      |> Enum.map(&resolve(&1, room_events))
+      |> Enum.map(&resolve(&1, room_events, apply_state))
 
     resolved_state = do_resolve(state_sets, room_events)
     # TODO: check if state event
@@ -55,6 +55,7 @@ defmodule MatrixServer.StateResolution do
   end
 
   def do_resolve(state_sets, room_events, unconflicted_state_map, conflicted_state_set) do
+    # TODO: make the state set a hashmap instead of a set.
     full_conflicted_set =
       MapSet.union(conflicted_state_set, auth_difference(state_sets, room_events))
 
@@ -82,8 +83,8 @@ defmodule MatrixServer.StateResolution do
 
     conflicted_control_events_with_auth_ids
     |> MapSet.difference(full_conflicted_set)
-    |> Enum.map(&room_events[&1])
     |> Enum.sort(mainline_order(resolved_power_levels, room_events))
+    |> Enum.map(&room_events[&1])
     |> iterative_auth_checks(partial_resolved_state, room_events)
     |> Map.merge(unconflicted_state_map)
   end
@@ -205,8 +206,9 @@ defmodule MatrixServer.StateResolution do
       |> Enum.with_index()
       |> Enum.into(%{})
 
-    fn %Event{origin_server_ts: timestamp1, event_id: event_id1} = event1,
-       %Event{origin_server_ts: timestamp2, event_id: event_id2} = event2 ->
+    fn event_id1, event_id2 ->
+      %Event{origin_server_ts: timestamp1} = event1 = room_events[event_id1]
+      %Event{origin_server_ts: timestamp2} = event2 = room_events[event_id2]
       mainline_depth1 = get_mainline_depth(mainline_map, event1, room_events)
       mainline_depth2 = get_mainline_depth(mainline_map, event2, room_events)
 
@@ -344,4 +346,21 @@ defmodule MatrixServer.StateResolution do
     event_id = state_set[{"m.room.create", ""}]
     room_events[event_id].sender == user
   end
+
+  def is_authorized_by_auth_events(%Event{auth_events: auth_event_ids} = event) do
+    # We assume the auth events are validated beforehand.
+    auth_events =
+      Event
+      |> where([e], e.event_id in ^auth_event_ids)
+      |> select([e], {e.event_id, e})
+      |> Repo.all()
+      |> Enum.into(%{})
+
+    # TODO: make the state set a mapping to Event struct.
+    state_set = Enum.reduce(auth_events, %{}, fn {event_id, %Event{type: type, state_key: state_key}}, acc ->
+      Map.put(acc, {type, state_key}, event_id)
+    end)
+
+    is_authorized(event, state_set, auth_events)
+  end
 end